HOW SPONGES LIVE. 49 
the strength to tear it away; and tin I] g no 
further protection, are made entirely of .soft fibre. 
Here we must leave the history of s] I and 
their lives. We have left much unsaid, for to tell 
how sponges may increase by dividing or by budding, 
as well as by eggs, would have taken us too far into 
detail ; neither could we give space to trace the 
wonderful way in which the various spicules are 1 
as weapons of defence ; and for special examples of 
the different kinds of sponges you must consult works 
on natural history. We have had one chief object in 
view, namely, to sec how Life in this new form 
advanced beyond the earliest slime-animals. The 
sponge, with its two forms of cells and its division of 
labour, stands already far above the microscopic 
beings of our last chapter. Rooted to the rocks, and 
large enough to invite the attacks of enemies, it has 
yet learnt to protect itself by wonderful structu 
to distribute its food throughout a large body, and 
last, but not least, no longer to form its si 
merely of flint or lime, but to manufacture in its own 
body the material with which it builds. 
It has indeed succeeded so well that 1 V. B 
bank', one of the best authorities on sponge life, came 
to the conclusion that sponges are able to , 
almost entirely, during their lifetime, from k 
the i'ood of other animals. It is only 
death that their slime serves to nourish Is of 
minute creatures, and then the wonderful 1 
with which the living matter is 1 . uite 
enough to prove to us how well the In 
must have used its weapons I 
still it w as one o[ Life's living 1 n. 
